Open Day at Happy Valley with Keith Conlon

For just over a century, Happy Valley reservoir has been a vital link in Adelaide's water supply. A decade ago, it became the site for the city's biggest water treatment plant Ð and the complex is on show during a rare Open Day on Sunday 21 March.

The suburbs have crept past the wide sheet of water in the last twenty five years or so, but when the long earth wall was built across a shallow valley in the 1890's, it brought a burst of industry to a tiny village 15 kilometres south of Adelaide.

It is not a big reservoir in size or volume. Mt. Bold, for instance, holds four times as much water. Happy Valley is, in fact, a holding pond with about fourteen day's supply for nearly half a million people stretching from Moana in the South, all along the stretch of beaches to West Lakes in the north western suburbs. The Victoria Square fountain spurts Happy Valley water Ð it also serves the city square mile.

A large water reserve round it evokes the original stringy bark and wattle scrub, and the reservoir's watery fingers caress river red gum lined banks. The century old views contrast with the scientific precision and concrete of the modern water treatment plant.

With each customer taking a couple of 44 gallon drums full of water from their taps each DAY on average, the tank system is necessarily on a grand scale.

At the end of the summer, most of the reservoir supply comes through the Murray pipeline. In the case of Happy Valley, the water has been injected into the Onkaparinga River near Hahndorf, and has come down via Mt. Bold reservoir and the Clarendon weir. Its final passage is through a 5 kilometre tunnel cut when the reservoir was built.

After a short stay in the Happy Valley big pond, our aqua vitae enters the process plant, where much flocculation takes place. Alum, a coagulant, is added to precipitate the mud of the Murray and natural organisms into big particles in 'flocs'.

After a steady stir in the first tanks, the water enters four vast concrete tanks. It is already looking more of an ocean blue as the solids settle to the bottom over two hours. Moving bridges span the sedimentation tanks, it flows over controlled weirs into 16 open rapid gravity filter tanks. They look like very deep backyard pools, only these have 1 metre of sand at the bottom. That's the filter.

Bacteria and algae slip through the gaps, of course, and so chlorine is added to disinfect the water supply. Fluoride to required Health Commission levels goes in here too, adding a tooth decay zapper to each glass of water we drink.

Last stop on site at Happy Valley is the storage tank. There are two dug into the ground, holding 100 million litres each. A synthetic cover called hypalon floats on top, protecting the harvest from dust, bird droppings and other contaminants.

Across the metropolitan area, we're getting through the equivalent of five of those tanks each day. A holding tank that size would be as big as the Football Park stadium, with sides about one hundred metres high!

The plant and the reservoir at Happy Valley are owned by the public through SA Water. They're managed and operated by an international consortium, United Water. And both organisations invite you to the Open Day on Sunday 21 March from 1 Ð 4 pm.

Happy Valley and Hope Valley water treatment plants are open, and so are the Christies Beach and Bolivar waste and water treatment works. For more infomation you can call SA Water on 1300 650 950 or email info@postcards.sa.com.au